I could use some help with identifying the proper wiring set up on the fuel selector switch for my 1987 Chevy truck. It as of right now only uses the left side tank. If I switch to the other tank the truck quits running. Can anyone help me with this?
I would check the switch valve first. Get under the truck and have someone throw the switch and see if the valve is making noise.
Two options; disconnect the wiring harness off the pollak valve and use a test light to map it out. If you have power on two separate wires (when switched) everything on the truck is fine, change the pollak valve. 2 Take the switch out of the dash, unplug it, use a test light to find the hot and then jump them to bypass the switch and see if the valve moves. 87 fuel tank wiring is a unique year since they went to fuel injection that year, but the pollak valves are the same as the previous years. 87 tank switches are unique to only that year too. I think the below diagram will help.
If you have power on both legs when switched, and you hear the valve moving when you switch it, your problem is probably a bad in-tank fuel pump.
